Internal combustion engines operating under the principle of the Miller cycle usually have an open inlet port during the beginning of the compression phase of the combustion chamber(s). In a reciprocating engine, the Miller cycle may be obtained through timing of the opening of the inlet valve. In a rotary engine such as a Wankel engine, the Miller cycle may be obtained through proper positioning of the inlet port. The Miller cycle engine usually has a volumetric compression ratio lower than its volumetric expansion ratio.
Typically, the Miller cycle engine is used with a turbocharger to prevent loss of air during the beginning of the compression phase and to increase the pressure compression ratio. However, during the beginning of the compression phase when the inlet port is open, compression must be typically performed against the pressure of the turbocharger, which usually creates pressure losses.